The invention described herein was made in the performance of official duties by an employee of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon.
The invention relates generally to the automation of numerical analysis problems, and more particularly to an automated system for calculating magnetic stray field data associated with current loop configurations. The system provides the user with choices of input and output scenarios so that a variety of current loop designs can be evaluated with the same tool.
As is known in the art, the magnitude M of the magnet dipole moment vector of a wire shaped in the form of a rectangular loop and having electric current flowing therethrough is determined by the product
M=A*N*i
where A is the area enclosed by the rectangular loop, N is the number of turns of the loop, and i is the electric current flowing through the loop. For current loops with a small number of turns enclosing different areas, the magnetic dipole moment is calculated as the summation of the individual currents multiplied by the individual loop areas. The direction of the magnetic dipole moment vector is always normal to the plane of the current loop as determined by the xe2x80x9cright hand rulexe2x80x9d.
Three sets of equations are available for calculating the magnetic dipole moment of a current loop. A first set of equations is used for current loop configurations that are designated as small loops. A second set of equations is used for current loop configurations that are designated as large normal loops. A third set of equations is used for current loop configurations designated as large narrow loops. Criteria for designation of a current loop configuration as being one of small, large normal or large narrow, and the corresponding sets of equations used to determine magnetic stray fields associated therewith, are described in xe2x80x9cMilitary Handbook, Design of Electrical Equipment with Small Stray Magnetic Fields,xe2x80x9d MIL-HDBK-802, July, 1990.
The predetermined criteria definitions used to designate a current loop configuration will be briefly described. The small loop designation applies in situations where the current loop""s length and width are relatively close to one another, but both are significantly smaller than the distance from the measurement point to any point on the current loop. The large normal loop designation applies in situations where both the current loop""s length and width are large relative to the distance from the measurement point to any point on the current loop. The large narrow loop designation applies in situations where, once again, the current loop""s size dimensions are large relative to the distance from the measurement point to any point on the current loop, but the current loop""s length-to-width ratio is also large.
In addition, certain applications (e.g., mine or underwater target detection, underwater cable or pipeline detection, etc.) require the evaluation of a stationary current loop as an observation or measurement point moves past the current loop. However, this capability does not currently exist in the art of magnet stray field calculation for current loops.
Accordingly, it is an object of the present invention to provide a system for calculating magnetic stray field data associated with current loop configurations.
Another object of the present invention is to provide a current loop evaluation tool that can present magnetic stray field data associated with current loop configurations.
Still another object of the present invention is to provide a system for calculating and presenting magnetic stray field data for a variety of current loop configurations and for a variety of calculation scenarios.
Yet another object of the present invention is to provide a system for calculating and presenting magnetic stray field data for a situation defined by a stationary current loop and a moving measurement or observation point.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a system is provided for calculating magnetic stray field data associated with current loop configurations. A graphical user interface utilizes a plurality of screens to define a current loop configuration. More specifically, a first screen provides for the entry of data associated with a small loop and second screen provides for the entry of data associated with a large loop. The designation between small loop and large loop is predetermined. Each of the first and second screens prompts a user to select i) one of three orthogonal dipole directions in which the current loop configuration is aligned, ii) units of measure associated with the current loop configuration, and iii) one of a plurality of calculation scenarios.
The calculation scenarios include i) a first scenario in which the current loop configuration is defined by a single-size current loop and the user is prompted to enter a distance from a center of the single-size current loop to a point of observation, physical dimension data associated with said single-size current loop, number of turns of the single-size current loop and an amount of current that is to be simulated, and ii) a second scenario in which the current loop configuration is defined by a non-uniform sized current loop and the user specifies a data input file that defines the non-uniform sized current loop as a plurality of rectangular loops. The data input file specifies a distance from a center of each rectangular loop and a point of observation, physical dimension data associated with each rectangular loop, number of turns for each rectangular loop and an amount of current that is to be simulated. A processor is coupled to the graphical user interface and is programmed to perform magnetic stray field calculations in accordance with the selected one of the calculation scenarios for one of the small loop and large loop as selected via one of the first and second screens.
In the second calculation scenario, each of the first and second screens provides the user with a first option to store results of the magnetic stray field calculations to an output file, a second option to display results of the magnetic stray field calculations for each of the rectangular loops, and a third option to display results of the magnetic stray field calculations as a cumulative value for all of the rectangular loops. The graphical user interface accesses a third screen for graphically displaying the results of the magnetic stray field calculations for each of the rectangular loops when the second option is selected. The graphical user interface displays the cumulative value on one of the first or second screens when the third option is selected.
A third calculation scenario can be provided by the present invention. In this third scenario, the current loop configuration is defined as in the first scenario except that the user utilizes the graphical user interface to access a fourth screen via one of the first and second screens. The fourth screen prompts the user to select a movement direction from the three orthogonal dipole directions. The movement direction defines a direction of simulated movement past the current loop configuration. The user is also prompted to enter start and stop positions along the movement direction as well as a step increment. The magnetic stray field calculations are then performed along the movement direction at each step increment between the start and stop positions. Calculation results are determined relative to each of the three orthogonal dipole directions. The fourth screen graphically displays the results of magnetic stray field calculations at each step increment relative to each of the three orthogonal dipole directions.